DIETARY LIPIDS MODULATE BONE PROSTAGLANDIN E-2 PRODUCTION, INSULIN-LIKE GROWTH-FACTOR-I CONCENTRATION AND FORMATION RATE IN CHICKS

This study examined the effects of dietary fat on the fatty acid compo sition of liver and bone, and on the concentration of insulin-like gro wth factor-I (IGF-I) in liver and bone, as well as the relationship of these factors to bone metabolism. Day-old male broiler chicks were gi ven a semipurified diet containing one of four lipid sources: soybean oil (SBO), butter + corn oil (BC), margarine + corn oil (MAC), or menh aden oil + corn oil (MEC) at 70 g/kg of the diet. At 21 and 42 d of ag e, chicks fed MEC had the highest concentration of (n-3) fatty acids [ 20:5(n-3), 22:5(n-3) and 22:6(n-3)] in polar and neutral lipids of cor tical bone but the lowest amount of 20:4(n-6) in polar lipids. Diets c ontaining t-18:1 fatty acids (MAC and BC) resulted in t18:1 accumulati on in bone and liver. Bone IGF-I concentration increased from 21 to 42 d in chicks given the SBO and BC diets. Tibial periosteal bone format ion rate (BFR) was higher in chicks given BC compared with those consu ming SBO and MEC at 21 d. The higher BFR and concentrations of hexosam ine in serum and IGF-I in cartilage, but lower 20:4(n-6) content in bo ne polar lipids in chicks given BC compared with those given SBO sugge st that BC optimized bone formation by altering the production of bone growth factors. A second study confirmed that dietary butter fat lowe red ex vivo prostaglandin E-2 production and increased trabecular BFR in chick tibia. These studies showed that dietary fat altered BFR perh aps by controlling the production of local regulatory factors in bone.